DESCRIPTION: Wound healing is a complex process that follows a defined sequence of events consisting of inflammation, proliferation and migration of epithelial cells to re-epithelialize the wound, and remodeling/differentiation. The cationic antimicrobial protein of 37 kDa (CAP37) belongs to the innate immune system and was originally identified based on its powerful antimicrobial effect. It was later found to induce migration, adhesion and proliferation of cultured corneal epithelial cells, which translated into faster corneal re- epithelialization in vivo. Structure-function studies of CAP37 were initiated with the long-term goal to identify the antimicrobial and the wound healing domains of the protein to generate therapeutic peptides for clinical use. Our lab recently identified two CAP37-derived peptide analogs that carry a strong antimicrobial activity, even on antibiotic resistant or multiresistant strains, and a wound healing activity. These analogs have strong potential to be used as innovative ocular treatments with the dual effects of promoting corneal re- epithelialization and preventing or clearing bacterial infections. The molecular mechanisms mediating the wound healing effects of the full length CAP37 and the two derived analogs are unknown. The objective of this proposal is to identify the membrane and intracellular mediators activated by these extracellular ligands to induce migration of immortalized corneal epithelial cells and corneal re-epithelialization in mouse. Based on previous studies in our lab, we hypothesize that CAP37 and derived analogs act as extracellular ligands, binding a G protein-coupled receptor (GPCR) on corneal epithelial cells to activate intracellular signaling pathways, including the signal transduction proteins PKC? and PKC?, thus promoting wound healing effects. Two specific aims are proposed. (1) To identify the receptor(s) mediating the migration of human corneal epithelial cells and corneal wound healing in response to CAP37 ligands. (2) To identify the downstream signaling pathway(s) mediating corneal epithelial cell migration and corneal wound healing in response to CAP37 ligands. This new knowledge will break new grounds in this field of research because a receptor for CAP37 will be identified for the first time since its discovery 30 years ago. This new knowledge will also be key to developing and optimizing CAP37-derived peptide analogs into innovative therapeutics with the dual effects of killing resistant pathogens and promoting wound healing.